MXPA01004485A - Mixing system for separation of materials by flotation - Google Patents

Abstract

A mixing system for a flotation tank (10) includes a radial flow impeller (24) and an axial flow impeller (26) which are attached for rotation on a common shaft (32), with the axial flow impeller (26) below the radial flow impeller (24).

Description

MIXING SYSTEM TO SEPARATE MATERIALS BY FLOTATION DESCRIPTIVE MEMORY The present invention relates to mixing systems that are specially adapted for flotation separation of different species of materials, such as minerals contained in naturally occurring minerals, and particularly to a mixing system that minimizes the energy used to carry out the flotation separation procedure. It is a main feature of the invention to provide a mixing apparatus that maintains a solid suspension in circulation of the materials, which disperses a ventilation medium (air or a gas) in the solid suspension in circulation, and mixes and combines the suspension with the air, while maintaining circulation in a contact area where the material that is to be separated joins the bubbles of the ventilation medium, whose zone is separated from a zone with little activity or at rest through which the bubbles can rise and form a floating foam, reaching the surface without breaking and releasing the particles that are to be separated. The mixing apparatus is in a tank that contains a liquid and particles of the material (minerals in the natural state and waste with which the minerals are extracted in the natural state). The liquid that is suitably water is included, which contains additives that promote the hygroscopic bonding of particles of the materials to be separated by flotation. The tank and the mixing apparatus therein may also refer to flotation cells. To perform flotation separation effectively and efficiently, gas dispersion in the form of bubbles, solid suspension and mixture combining solid suspension and bubbles is required. In addition, the region in the tank where the circulation of the solid suspension is carried out and is in contact between the bubbles of the ventilation medium and the particles so that the species of material to be separated can adhere to the bubbles, called contact zone, desirably separates from the area of the tank, above the contact zone, through which the bubbles can rise without breaking and releasing the particles they carry (an area with little or no activity). repose). It is a feature of the invention to provide for the suspension, dispersion of the ventilation means in the form of bubbles and combination and mixing, as well as separation in contact zones and with little activity all with an efficient use of operation power that activate the apparatus of mixed, thus reducing the energy required to carry out the flotation separation process. The flotation separation cells have mixing mechanisms included with various combinations of special impellers to obtain dispersion and gas combination, but have not achieved the energy utilization efficiency that is desired. For example, Booth ,. patent of E.U.A. 2,875,897 issued March 3, 1959, has used a special impeller by means of which the gas is induced by induction. An axial flow impeller pumps up and discharges flow directly into the gas-induced impeller. The provision is against the use of efficient energy as well as the effective separation of contact zones and areas with little activity. Special deflector and suction pipe arrangements around the arrow, sometimes called ancillary elements, have been used to separate the zones. See, for example, the Booth patent, Krishnaswany, et al., E.U.A. 4,800,017, January 24, 1989 and Kallioinen, et al., E.U.A. 5,039,400, August 13, 1991 and in the Wemco flotation machines marketed by Eimco Processing Equipment of the city of Salt Lake Utah, E.U.A. It is a principal object of the present invention to provide an improved mixing apparatus that effectively performs flotation separation of different species of materials with high efficiency, for example, reducing the energy required in conventional flotation machines from 14920 joules / second to .0038 liters or more, up to 1492 to 3730 joules / second per .0038 liters. It is another object of the present invention to provide an improved flotation separation apparatus in which the solid suspension and circulation of the suspension is obtained with an axial downflow pump impeller that scavenges the solids that conglomerate in the lower part of the tank and circulate the solids that passed the gas bubble discharge from the radial flow impeller to maintain separate contact and zones at rest in the tank, thus improving and making efficient in terms of energy consumption, the flotation separation process. It is still another object of the present invention to provide an improved mixing apparatus that increases the efficiency of the flotation separation process using a radial flow gas dispersion impeller, which operates efficiently by maintaining the impeller in its entirety or substantially in part. in the gas that disperses, thus reducing the energy requirement for gas dispersion in the flotation separation process. It is still another object of the present invention to provide an improved mixing apparatus that provides circulation in a tank or flotation separation cell about a downward path through the gas while it is dispersed from another impeller, subsequently through the bottom of the tank thus avoiding a short circuit in the lower part of the tank or the circulation path through the dispersion gas, and further improving the efficiency of the flotation separation process in terms of the energy required to provide contact between the materials of circulation and gas dispersion bubbles. As briefly described, the mixing apparatus for the selective separation of different species of flotation particulate materials, according to the invention, makes use of means for providing a generally radially directed flow of bubbles from a venting medium to a liquid medium in the tank. Other means are provided for circulating a suspension of the materials along a generally downward path to the bottom of the tank and through the radially directed flow of the venting medium to define a contact zone below a zone at rest in the tank, in which the particles of the contact zone of the selected species of the materials hygroscopically attached to the bubbles of the ventilation medium float with the bubbles in the area with little activity for collection, when they reach the surface of the liquid medium in the tank. The foregoing and other objects, features and advantages of the invention, as well as the preferred embodiments thereof, will be apparent from reading the following description in connection with the accompanying drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of the mixing apparatus provided by the invention in a flotation separation tank. Fig. 2 is a sectional plan view taken along line 2-2 in Fig. 1. Fig. 3 is another sectional plan view taken along line 3-3 in Fig. 1.

Figure 4 is an enlarged view of the radial and axial flow impeller of the mixing apparatus shown in Figure 1. Figure 5 is a plan view along line 5-5 in Figure 4. Figure 6 is a schematic diagram illustrating flow and flow patterns obtained by arranging the impellers shown in Figures 1-5. Figure 7 is an elevational view similar to Figure 4, illustrating the mixing apparatus including a radial flow impeller of a type other than the impeller shown in Figures 1-5, in accordance with another embodiment of the invention. the invention. Figure 8 is a sectional plan view taken along line 8-8 in Figure 7. Figure 9 is an elevation view similar to Figure 4, showing a radial flow impeller of a type other than the impeller shown in Figures 4 and 7, and in accordance with yet another embodiment of the invention. Figure 10 is a sectional view taken along line 10-10 in Figure 9. Figure 11 is an elevation view similar to Figure 1, showing an arrangement of two axial flow drivers in the same arrow as the radial flow impeller, in accordance with yet another embodiment of the invention; and Figure 12 is a diagram illustrating the variation in energy utilization in terms of energy number, Np, as a function of flow in SCFH (in a flow in liters per hour at standard temperature and atmospheric pressure), for different spacings between the upper edge of the radial flow impeller shown in Figures 1-5 and the stationary flange of the air supply line which, with the rotating disc along the lower edge of the impeller, defines a space for the introduction of air and the discharge of air in the form of bubbles. Referring to Figures 1-5, a flotation cell provided by means of a tank 10 is shown. This tank contains a liquid medium, such as water. Can be added to this medium chemicals which promote hygroscopic attraction of metallic ores in their natural state to be separated into bubbles then rise to the top 12 or level of liquid in the tank 10 where they float, forming a foam which is collected, for example, by flowing over an annular pourer 14 in an annular collector tank 16. A defoamer may be used to move the foam towards the pourer 14, but is not shown in the illustration. The flotation bubble foam contains concentrated natural mineral that is separated from other particles, sometimes called waste, which can be decanted from the lower part 18 of the tank by means of pumping discharge (not shown). The walls of the tank can have mounted on the same baffles 20. There can be four deflectors separated by 90 °. The upper ends 22 of the deflectors are placed below the liquid level 12. The mixing apparatus uses a radial flow impeller 24 and an axial flow impeller 26. These impellers have hubs 28 and 30 that are attached to an arrow 32 which rotates both impellers 26 and 24 about the same axis of rotation. The diameter of the axial flow impeller 26 as measured between the tips 34 of its blades 36, may be 30 to 40 percent of the diameter of the tank as measured between the inner part of the vertical wall 38 of the tank. The arrow 32 is driven by an impulse mechanism 40 which may include a gearbox. This mechanism rests on a transverse beam 42 on top of the tank 10. The arrow extends to the lower part 18 of the tank so that the coaxial flow impeller is placed with its midline 44 of 3/8 from D to 1 of D (where D is the diameter of the impeller 26) away from the lower part 18 of the tank. This space is an example of sufficient space to obtain circulation from the axial flow impeller when it is pumped downward sweeping through the bottom of the tank as will be explained in more detail herein in relation to figure 6. The impeller of radial flow 24 is positioned so that its median line 46 is suitably D / 2 from the midline 44 of the axial flow impeller 26. This separation of D / 2 is an example of a sufficient space so that circulation descending in the axial flow impeller 26 is wound around the discharge from the radial flow impeller. By crossing the discharge flow from the radial flow impeller, the contact between the air bubbles or other means of ventilation that is discharged radially from the impeller 24, can make contact with the particles of the mineral in the natural state that are to be separated for the hygroscopic bonding of these particles to the bubbles. The bubbles subsequently float through the contact zone 48 defined by the circulation path or flow from the axial flow impeller and rise through an area with little activity 50 above the contact zone to form the foam that floats at the liquid level or the surface 12. A perforated circular plate 52 resting on a ring 54 is placed in the resting zone. The perforations in the grid 54 allow the bubbles carrying the particles to be separated to pass through it while delineating the separation of the contact zone 48 from the resting zone 50. Around the arrow 32, it is found a hollow pipe 56 closed in the upper part 58 thereof and having a disc-shaped flange 60 in the lower part thereof. The pipe 56 and the flange 60 are fixed, as if they were attached to the beam 42 or otherwise secured to the wall 38 of the tank 10. The radial flow impeller 24 has a plurality of blades of the flat plate 62. They are six vanes 62, extending radially at 60 ° C. These vanes have upper and lower edges 64 and 66. The lower edges are joined to a disc 68. The diameter of the disc is equal to the diameter of the impeller 24. The diameter of the impeller 24 and the flange 60 are approximately equal to each other. The upper edges 64 of the vanes and the lower surface of the flange 60 are separated by a play space 70. This space in the embodiment shown in Figures 1 to 5 is sufficient to provide a set for the rotation of the impeller 24 without interfering with disc 60. The game may vary, for example, from 0.15 cm to 1.27 cm depending on the impeller 26 D, depending on the shear force mechanism that forms the bubbles that are desired, and also depending on the energy to rotate the impeller you want to use. This relationship is illustrated in Figure 12, for various energy numbers and flow numbers, by a family of curves for spaces of varying size from 0.15 cm to 1.27 cm. The impeller 26 D is about 50.8 cm for the data shown in figure 12. The disk 68 rotating with the impeller 24 and the fixed disk flange 60 define a space in which the gas flows through the hollow interior 71 of the pipe 56. The gas can be pressurized gas (above the top pressure in the space between the flange 60 and the disk 68 below the liquid level 12 which is coupled by means of a side pipe 72). The gas can be introduced by induction due to the suction formed by the radial flow impeller 24. Subsequently the side pipe 72 can be an open pipe. The gas flow can be clogged by a suitable valve in line 72 (not shown). When the lining between the flange 60, and the disc 68 is sealed essentially due to the minimum separation in the space 70, then the space between the flange 60 and the disc 66, which is essentially filled by the blades 62, contains only so essential air. This improves efficiency and is manifested by a lower energy number Ne as illustrated in Figure 12. Subsequently, the bubbles are cut mechanically at the intersection of the tips 76 of the radial blades and the liquid in the tank. It may be desired to introduce fluid or hydraulic shear, in which case the separation of the space 70 is increased by allowing liquid to be found in the space between the flange 60 and the disk 68. Subsequently the liquid is pumped radially with the gas. Due to the difference in flow velocities of the liquid and gas, a hydraulic shear stress of the gas is generated in the bubbles which is in addition to the mechanical stress at the tips 76. The advantage of using hydraulic shear stress is the additional energy consumption as will be apparent from FIGS. 12. The radial flow driver 24 may be of the R300 type available from Lightnin Mixers of 135 Mt. Read Blvd., Rochester, New York 14611, E.U.A. The R300 impeller includes the blades 62 and the disc 68 and the hub 28. The disposition of the R300 in an inverted position to form the space thus providing an improved power consumption in air handling is an important feature of the present invention. The axial flow impeller illustrated by way of example in the drawings is the A310 impeller also available from Lightnin Mixers. This impeller is described in Weetman, patent of E.U.A. 4,486,130, August 23, 1984. Other axial flow impellers can be used. However, the A310 impeller is preferred due to its efficiency in terms of power consumption. The diameter as measured at the tips of the impeller 26 is greater than the diameter of the radial flow impeller 24. Preferably, the diameter of the impeller 26 is about 1.5 times the diameter of the radial flow impeller 24. This ratio in size and the space between the axial and radial flow impellers are selected to provide the circulation path defining the contact zone 48 and the separation of the zone 48 from the zone with little activity 50. As shown in figure 6, the current of gas bubbles 80 expands as the stream is discharged radially from the radial flow impeller 24. The downflow pumping axial flow impeller 26 drives the flow downwardly toward the lower portion 18 of the tank 10, where the flow sweeps any particle that is collected or conglomerates at the bottom 18. Subsequently the flow runs its course along the wall 38 of the tank directed by the deflectors 20 and returns to the downstream to the inner side of the impeller. In other words, the pressure side of the impeller 26 faces downwards while the suction side faces upwards. The suction side subsequently pushes the flow down through the impeller where it circulates around in the path 80. It will be appreciated that this path extends annularly around the tank 10. The path traverses the discharge stream of the bubbles 80 as the discharge current expands. As the flows are traversed and combined, the particles of minerals in the natural state (selected species) transported with the flow are collected with the bubbles. The bubbles adhere to the minerals in their natural state due to the hygroscopic attraction. Some of the bubbles circulate around the path while others rise with particles bound through the area with little activity to the surface of the liquid level 12 where they are collected as foam and can flow, for removal, over the spillway. in the collection tank 16. With reference to figures 7 and 8, the radial flow impeller 90 is of the R100 type, also available from Lightnin Mixers. This impeller has a central disk 92 to which the blades 94 are attached. This disk and the lower surface of the flange 60 form the space in which the gas is introduced by passage 71 and the hollow pipe 56. The upper edges 98 of the blades 94 are separated from the undersurface of the flange 60 sufficiently to provide a play space that does not interfere with the rotation of the impeller 90. The impeller 94 operates in the liquid in the tank and provides a hydraulic shear stress to form the bubbles. Preferably, the air is introduced into the space between the flange 60 and the disc 92 under pressure as in the external compressor. Otherwise, the mixing apparatus is similar to the apparatus described in relation to Figures 1 to 6. Referring to Figures 9 and 10 there is shown a radial flow impeller 100 which may be of the R130 type which is also available from Lightnin Mixers. This impeller includes 6 blades that are arched and form hemicilindrical tips 102. The tips 102 are tangential to the radial lines extending from the axis of the arrow 32. The tips102 are joined to the central disk 104 whose lower surface of the flange 60 provides a space in which air is introduced through the hollow pipe 56. This air is preferably pressurized, from an external compressor. The upper edges of the blades of the tip 102 are spaced apart by space 70 from the flange 60 to provide sufficient space only for the play space for free rotation of the impeller 100. The gas is introduced into the space between the disk 104. and the flange 60 and discharge radially outwards. The tips of the tip 102 also operate in liquid and provide a pumping of radial liquid causing hydraulic shear stress of the gas as well as mechanical shear to obtain the discharge of the bubbles. Otherwise, the operation of the mixing apparatus shown in Figs. 9 and 10 is similar to the apparatus described in relation to Figs. 1 to 6. Fig. 11 illustrates a system wherein the radial flow driver 24 can be located further. up in the tank compared to the case of the system shown in Figures 1 to 10. When placing the highest radial flow impeller in the tank, the hydraulic head in the depth of the radial flow impeller is smaller than in the case of the previously illustrated systems, thereby improving gas flow by suction due to the need to overcome a smaller pressure head in the space between the flange 60 and the disk 68. To provide the circulation which sweeps through the lower part of the tank to collect the particles and place them in suspension in the liquid in the tank, mount a pair of axial flow impellers 110 and 120, both of type A310, in the arrow 32. Both booster s are pumped down and increase the length in the vertical direction in tank 10, of the circulation path. Even so, a zone of little activity is obtained, nevertheless that zone is smaller than the contact zone where the circulation takes place. From the above description it will be apparent that an improved mixing apparatus and system is provided, especially suitable for use in the flotation separation process. Variations and modifications of the mixing apparatus described herein and the flotation mechanisms in which they are used, of course, become apparent to those skilled in the art. Also, the above description should be taken as illustrative and not as limiting.

Claims (22)

NOVELTY OF THE INVENTION CLAIMS

1. - A mixing apparatus for selective separation of different species of particles by flotation comprising means for providing a flow generally directed radially of bubbles of a venting medium in a liquid in a tank, said tank has a wall that is extends from the upper part to the lower part thereof, means for providing circulation of a suspension of said materials along a generally downward trajectory towards the lower part of the tank and through said radiated directed flow, said circulation includes said flow descending and an upward flow along said wall to define a contact zone below a zone at rest in said tank where said contact zone particles of the selected species of said materials hygroscopically attached to said bubbles flow with said bubbles in said area at rest for collection when they reach the super of said liquid in said tank.

2. The mixing apparatus according to claim 1, further characterized in that the radially directed flow provides means comprising a pair of plates defining a space with which an inlet for said ventilation means is in communication, one of said plates is a plate that is rotatably connected to blades of the radial flow impeller placed in said space.

3. The mixing apparatus in accordance with the claim 2, further characterized in that one of said plates is a flange of a conduit through which said ventilation means flows in said space, whose conduit is fixed relative to said impeller.

4. The mixing apparatus in accordance with the claim 3, further characterized in that said venting means is externally pressurized from said duct to flow in said space or flows therein by suction created by said radial flow impeller.

5. The mixing apparatus in accordance with the claim 4, further characterized in that the fixed flange has a diameter approximately equal to the diameter of said impeller.

6. The mixing apparatus according to claim 2, further characterized in that the radial flow impeller has a plurality of vanes having upper edges spaced from the lower edges therein in a direction separate from the lower part of the tank, the other plate is not rotatable and is separated above said rotating plate, said non-rotating plate is sufficiently close to said rotary plate to restrict the flow of liquid medium in said space while said impeller rotates while providing play space from said rim upper of said radial flow impeller to allow rotation thereof.

7. - The mixing apparatus in accordance with the claim 6, further characterized in that the space of said non-rotating plate of said upper edges is selected from the near space which essentially excludes said liquid medium from said space to a space to allow said liquid medium to enter said space to be activated radially to impart hydraulic shearing force to said ventilation means thus helping to inflate the bubbles.

8. The mixing apparatus in accordance with the claim 7, further characterized in that said rotating plate is a coaxial disc with and of approximately the same diameter as said radial flow impeller and positioned along the lower edges of said impeller blades.

9. The mixing apparatus according to claim 7, further characterized in that said rotating plate is a coaxial disc with said axial flow impeller and intermediaries placed on the upper and lower edges thereof, said upper edges of said The impeller has play spaces from said non-rotating plate sufficient only to allow rotation thereof.

10. The mixing apparatus according to claim 9, further characterized in that said disk has a diameter smaller than the diameter of said radial flow impeller and of the non-rotating plate, and said vanes extend radially after said rotary disk.

11. The mixing apparatus according to claim 9, further characterized in that said blades are selected from the group consisting of a plurality of flat bands and a plurality of curved bands, said curved bands forming tips that define surfaces that are generally extend tangentially to a rotational access of said impeller.

12. The mixing apparatus according to the claim 1, further characterized in that said circulation providing means is at least one axial flow impeller which operates to pump down towards the bottom of the tank and with a space of about 3/8 of D to 1 D from the lower part of the tank. tank, where D is the diameter of the axial flow impeller.

13. The mixing apparatus in accordance with the claim 12, further characterized in that said circulation providing means is at least one axial flow impeller which operates to pump down towards the bottom of the tank and with a space of about 3/8 of D to 1 D from the bottom of the tank. tank, where D is the diameter of the impeller, and said axial flow impeller rotates in the same arrow about the same axis as said radial flow impeller and is located sufficiently close to said axial flow impeller to provide a flow of entrance therein that includes the discharge flow from said radial flow impeller and is not separated therefrom.

14. The mixing apparatus according to the claim 13, further characterized in that said diameter of said axial flow impeller is larger than the diameter of said radial flow impeller.

15. - The mixing apparatus according to claim 14, further characterized in that the diameter of said axial flow impeller is about 1.5 times the diameter of said radial flow impeller.

16. The mixing apparatus according to claim 13, further characterized in that said axial flow impeller is separated approximately 1/2 of D along said arrow away from said radial flow impeller where D is the diameter of said axial flow impeller.

17. The mixing apparatus according to the claim 16, further characterized in that said axial flow impeller separates about 1/2 diameter along said arrow away from said radial flow impeller where D is the diameter of said axial flow impeller.

18. The mixing apparatus according to claim 12, further characterized in that a plurality of said axial flow impellers rotate on an arrow and a lower thereof has said space above the bottom of the tank.

19. The mixing apparatus for combining different fluid means comprising means for providing flow directed generally radially of a first fluid means in a second fluid medium in a tank, said tank having a wall extending from the upper part to the lower part thereof, means for providing circulation of both the first and the second fluid means along a generally downward trajectory towards the lower part of the tank and through said radially directed flow, said circulation includes said flow descending and an upward flow along said wall to define an area in said tank in which said fluid means are mixed.

20. The mixing apparatus according to claim 5, further characterized in that said radially directed flow providing means comprises a pair of plates defining a space with which an inlet for said ventilation means is in communication, a tt of said plates is a plate that is rotatably connected to the blades of the radial flow impeller placed in said space.

21. The mixing apparatus according to the claim 19, further characterized in that one of said plates is a flange of a conduit through which said first fluid means flows in said space, whose conduit is fixed relative to said impeller.

22. The mixing apparatus according to claim 15, further characterized in that said first means is externally pressurized from said duct to flow in said space or flows therein by suction created by said radial flow impeller.